The invention relates to a resilient mounting for a reclining seat which can apply a return bias to the seat when the seat is tilted relatively to a supporting base.
Many different types of resilient mountings for reclining seats have been proposed hitherto, some of which utilize one or more torsion bars to provide the return bias. The mountings usually include two pivotally interconnected members one of which carries the seat and the other of which attaches to the supporting base, the torsion bar merely serving to provide the return bias. Examples of such mountings are described in British Pat. Nos. 1,322,593; 1,161,464 and 811,283 as well as in others mentioned below. In each of those mountings the torsion bar providing the return bias passes through bearings provided between the two members to enable one to pivot relatively to the other. This arrangement necessitates the use of special bearings which not only interconnect the relatively tiltable members but which have also an internal bore shaped to receive the the torsion bar. The torsion bar is normally of square cross-section and so the bearings have a cylindrical outer periphery, around which one of the members can rotate, and a square cross-section internal bore. The use of such bearings not only increases the overall cost of production but makes assembly difficult.
In mechanisms such as described in British Pat. No. 1,425,363, the use of such bearings is avoided by utilizing coaxial bearing tubes arranged one within the other on the two members. The torsion bar passes coaxially through the innermost tube and is arranged to apply a return bias when one of the members is tilted relative to the other. Whilst the use of tubes avoids the need to manufacture special bearing elements, the product has to be assembled accurately in view of the need to align the various tubes coaxially.
An improved tilting mounting has been proposed in British Pat. No. 1,487,273. However the mounting still requires bearings for providing the pivotal connection between the fixed and tilting members. The bearings rotatably support tubes secured to the tilting member and the tubes house springs for providing the return bias. With this fitting, accurate alignment of the tubes is necessary during manufacture to ensure free pivoting of the tubes on the bearings.
The invention as claimed is intended to mitigate the foregoing disadvantages and, according to the invention there is provided a resilient mounting for a reclining seat, the mounting including a first member to be secured to a base for the seat, a second member to be secured to the seat and which is pivotally connected to the first member, and a torsion bar for providing a return bias when one of the members is tilted relative to the other, the resilient mounting being characterised in that the torsion bar interconnects the two members and forms the pivot.
The advantage offered by the invention is that the torsion bar not only provides the return bias but also forms the pivot, thus avoiding the need for bearings in addition to the torsion bar for pivotally interconnecting the first and second members. Therefore the resilient mounting is less complex than resilient mountings previously proposed.
In the prior patents referred to, the torsion bars described take up a considerable amount of space beneath the seat because they are straight from end to end. As a result, the torsion bars require long housings to accommodate them. Where the housings are in the form of steel tubes or castings the overall weight of the mountings can be considerable. Also, elongated housings projecting from a central assembly of first and second pivotally interconnected members tend to make the mounting somewhat cumbersome. In a preferred resilient mounting according to the invention, the torsion bar is made from a metal bar which is bent to form a first elongate portion which provides the pivot and a second elongate portion which extends generally alongside the first portion. The first portion may have a free-end portion which extends substantially at right angles thereto and abuts reaction means on the first member, and the second portion may also have a free-end portion extending substantially at right angles thereto and which abuts reaction means on the second member. Thus, the torsion bar is bent back on itself and does not require an elongated housing as would be the case with a completely straight torsion bar formed from a similar length of metal bar. This enables the torsion bar to be contained within a very compact housing beneath the seat. Such a compact housing results in a resilient mounting of comparatively less weight.
The use of a straightforward abutment surface on the first member leads to a particularly simple construction whereas, in some of the prior art devices, specially shaped retainers having square cross-section bores are necessary to provide reaction for square cross-section torsion bars.
In several of the prior art mountings, many of the moving parts are easily accessible even when the mounting is secured to the seat. Whilst this might appear prima facie advantageous, it is undesirable in at least two aspects namely:
(i) the user can be pinched by relatively moving members and PA0 (ii) the mechanism can become heavily caked with dust particularly where the moving parts are greased.
However, in the preferred embodiment of the invention, the second member is in the form of an open-topped tray which fixes to the seat so that the seat covers the open top and which wholly contains the first member, said first member, when the second member is secured to the seat, being accessible through an aperture in the floor of the second member, said aperture being in alignment with a portion of the first member which is to be secured to the supporting base for the seat. In this manner, the working parts are entirely housed within the second member and will, therefore, remain clean throughout the working life of the mounting. Also, with such an arrangement, it is almost impossible for the user to be pinched by relatively moving parts.
The second member can easily be made in tray-like form by using casting methods such as pressure die casting. This is advantageous over many of the prior art mountings which are in the form of heavy welded fabrications. The first member can also be a die casting.
Preferably the metal bar forming the torsion bar is bent so that the elongate first and second portions converge in the direction away from the bend. Such an arrangement causes the torsion applied to the torsion bar to be distributed substantially along the entire bar rather than being concentrated to a large extent at the bend. In this manner, the endurance of the torsion bar is greater than if, say, the first and second portions were parallel.
In another embodiment, the torsion bar may comprise a metal bar which is bent to form an elongate portion which provides the pivot and has two free-end sections which are bent substantially at right angles thereto, one of said free end sections abutting reaction means on the first member and the other free-end section abutting reaction means on the second member. Such an arrangement provides a simpler form of torsion bar and still results in a compact mounting.
Straightforward assembly of resilient mountings is an essential prerequisite for efficient production. Where torsion bars have to be fed through a number of aligned bores, some of which are of square cross-section, there are assembly difficulties. A preferred form of mounting overcomes this problem to a large extent by providing cradle-like mounting means on the first and second members which locate the portion of the torsion bar which provides the pivot, the pivot-forming portion of the torsion bar being retained in the cradle-like mounting means by detachable retainers.
In order to ensure that the cradle-like mountings provide maximum bearing area, the cradle-like mountings on the first and second members provide aligned bearing surfaces which engage the pivot-forming portion of the torsion bar over the majority of its length.
A resilient mounting for a reclining seat in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: